Fixing errors (#DIV/0!) · Lập trình với Martin

An error is not a punishment — it is a signal

When a cell shows #DIV/0!, the formula divides by zero. The spreadsheet cannot do “infinity”. Something in the denominator is 0 or empty.

Other common ones:

Error	Meaning	Cause
`#DIV/0!`	divide by zero	`/0` or an empty cell
`#VALUE!`	wrong type	text + number
`#NAME?`	unknown function	a typo AVERGE
`#REF!`	a broken reference	a deleted sheet/row

💡

Click the cell with the error. A bubble with an explanation appears. In Excel a small yellow triangle. Read it — it often says which cell.

Make an error on purpose

Ghi chús G1 10, H1 0. I1 =G1/H1. Enter. #DIV/0!
Change H1 to 2. I1 shows 5. The error disappeared.
Delete H1 (empty). Empty = 0 for division. The error again.

A fix with an average

=AVERAGE(B3:B8) when all cells are empty → #DIV/0!. Add a grade or narrow the range.

When in the range there is text two → #VALUE!. Fix to 2.

IFERROR — hide an error nicely (không bắt buộc)

=IFERROR(G1/H1,"—")

English IFERROR. When division fails, it shows a dash instead of a bang. In Czech Sheets sometimes IFERROR, sometimes a local version. If it does not exist, fix the input — do not hide the error forever.

⚠️

IFERROR is not a data fix. If you hide #DIV/0! on an average of empty grades, you still have no grades. Data first, then maybe IFERROR for a nice display.

Pocket money — dividing average daily spend

A12 Average spend, B12 =SUM(C2:C8)/COUNT(C2:C8).

When C2:C8 are all zeros, SUM 0, COUNT 7 — result 0, not an error.

When =SUM(C2:C8)/COUNT(A2:A8) and A has text days — COUNT on A does not count text → 0 → #DIV/0!. Fix: divide by COUNT(C2:C8).

Find or make a formula with an error. Fix the input, not only the cell colour.
Check the average on Grades — no #REF! after inserting rows? Widen the range.

🏫 Grade average

One sheet, two columns: subject and grade. At the bottom a sum and an average.

💰 Pocket money

Rows = days, columns = income / spend / left.

📊 Class survey

One question, answers in one column, later a chart.

🏆 Mini dashboard

Three numbers at the top and one chart. Numbers as a link, not copied by hand.

Now you 💪

On purpose you saw #DIV/0! and fixed the divisor.
You know #VALUE! = text instead of a number.
The grade average does not show an error — or you know why (an empty range).
After inserting a row you checked ranges in formulas.
You know IFERROR as an optional wrapper — not a stand-in for data.

✅

Check: A red cell does not scare you. You know where to look.

What to take from this lesson

#DIV/0! = divide by zero or empty.
#VALUE! = text in numbers.
#REF! = a broken reference after a delete.
Fix the input, do not only hide the error.
A bubble by the cell explains the detail.